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Entropy 2019, 21(3), 328;

Can a Quantum Walk Tell Which Is Which?A Study of Quantum Walk-Based Graph Similarity

Dipartimento di Scienze Ambientali, Informatica e Statistica, Universita Ca’ Foscari Venezia, via Torino 155, 30170 Venezia Mestre, Italy
Department of Computer Science and Engineering, Southern University of Science and Technology, Nanshan District, Shenzhen 518055, China
Author to whom correspondence should be addressed.
Received: 31 January 2019 / Revised: 22 March 2019 / Accepted: 25 March 2019 / Published: 26 March 2019
(This article belongs to the Special Issue Quantum Walks and Related Issues)
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We consider the problem of measuring the similarity between two graphs using continuous-time quantum walks and comparing their time-evolution by means of the quantum Jensen-Shannon divergence. Contrary to previous works that focused solely on undirected graphs, here we consider the case of both directed and undirected graphs. We also consider the use of alternative Hamiltonians as well as the possibility of integrating additional node-level topological information into the proposed framework. We set up a graph classification task and we provide empirical evidence that: (1) our similarity measure can effectively incorporate the edge directionality information, leading to a significant improvement in classification accuracy; (2) the choice of the quantum walk Hamiltonian does not have a significant effect on the classification accuracy; (3) the addition of node-level topological information improves the classification accuracy in some but not all cases. We also theoretically prove that under certain constraints, the proposed similarity measure is positive definite and thus a valid kernel measure. Finally, we describe a fully quantum procedure to compute the kernel. View Full-Text
Keywords: quantum walks; graph similarity; graph kernels; directed graphs quantum walks; graph similarity; graph kernels; directed graphs

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Minello, G.; Rossi, L.; Torsello, A. Can a Quantum Walk Tell Which Is Which?A Study of Quantum Walk-Based Graph Similarity. Entropy 2019, 21, 328.

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